SQL Server Bottleneck Triage: How to Separate Signals from Causes

This article provides a detailed methodology for triaging SQL Server performance bottlenecks, emphasizing the critical distinction between observable signals (high CPU, I/O latency, blocking) and their underlying causes. It explains common pitfalls where teams mistake symptoms for root causes, such as attributing CPU pressure solely to capacity issues or I/O problems to storage faults. The article covers how CPU pressure can stem from poor query plans, outdated statistics, or excessive parallelism, while I/O issues may originate from inefficient queries or index design rather than storage hardware. Blocking is analyzed as a symptom of transaction design or concurrency problems, not just lock contention. The guide advocates for systematic analysis before committing to a solution, making it valuable for DBAs and IT professionals focused on SQL Server performance optimization.